Will budget airlines show up in my flight search results, or does a flight API only cover the big airlines?

Yes, budget airlines can show up alongside the major carriers, but it is not automatic and it depends on which flight content is switched on for your portal.

There are really two kinds of flight content. Most full service airlines sit inside the large central reservation systems, so once you have a connection to one of those you get a very wide spread of carriers in one go. A lot of low cost carriers do not sell through those systems at all, so they have to be reached through separate direct connections or through a source that bundles several of them together. That means the budget airlines your customers see are whichever ones your enabled sources actually carry, and the mix is different from one region to another. Some low cost carriers in your market may be available straight away, others may not be available to us at all, and that is a supplier decision rather than something we can change at our end.

It also helps to know that budget fares behave differently once they are booked. Bags, seats and meals are usually sold as paid extras rather than being included, the fare rules are tighter, and changes or refunds often have to be requested instead of being completed instantly on the portal. Payment handling can differ too, because some carriers expect the booking to be paid in a particular way, so the settlement will not always look like a normal airline booking in your reports.

The most useful thing you can do next is write down the routes and the specific airlines that bring you most of your sales, and share that list with us so we can confirm which of them your available sources cover before you go live.